Blower



MaY 12, l931- J. J. sTogTzEL 1,805,055

BLOWER Filed DeC. 27, 1926 i i ATTORNEY v tionship of parts, and generally speaking the I d rush ofair from the housing into the partial Pareniea May 12, 1931 t nIrl-1DSTATES PATENT oFFlci-:-

JOSEPH JOHN STOETZEL,-OF QUEENS VILLAGE, NEW YORK, ASSIGNOR T0 G & G

ATLAS SYSTEMS,NG., OF NENV .YORK, N. Y., A ACORPORATION 0F NEW YORK l BLOWER Application ledDecember 27,1926. Serial No. 157,182. Y

mony of similar basic characteristics y'and gov-v n erned by the same operating principles; yOne of these classes is the lpressure blower in i .10 which free atmospheric air is compressed-to the desired degreeV before reaching the discharge outlet,the compressed air being dis-y.

charged at thevoutlet at a velocity equal to the peripheral velocity of the rotor.r y,

Another class is the so-called fbooster7 blower in which the blower is inserted intermediate the ends of a conveying duct, as 1n transferring gas from Lone storage tank to another. The', booster blower may be supf plied with ,a filling stream-having a density equal to or greaterthan that of the atmosphere and may operate tocompress and propel, or merely to propel, the stream of gas assing therethrough. The third classis the evacuating blower 'in which the filling stream of air is supplied at a density below that of the atmosphere, the blower operating to compress the mass of air to the required density andy to discharge the air into atmosphere. f

It has been the standard practice among dii-ferent blower andfan manufacturers to make use of substantially the same formulas or ratios with respectrto the `sizes and relablower constructions heretofore provide have operated with a relatively low effi-l ciency. An example of a standard prior con struction is a pressure blower having a double fan wheel of twenty-seven inches diameter with intake openings in each sideipf .the casing of thirteen and one -half inches in diameter, or one half the diameter of the wheel. In this particular form of standardA construction the fan wheel is provided with eighteen vanes spaced equally distant from each other. The vanes have a widthat the intake end, (i. e., at the inner end), equal to twenty-five per cent of the diameter of the wheel and a width at the discharge orl outlet end equal to twelve and one half per cent ofy the diameter of the wheel.

With this particular structural arrangement, (similar ineiiicient arrangements being characteristic ofY other sizes and types of prior v constructions), it will be seen that, since'the vanes are separated at their tipy or discharge ends by substantially double lthe distance separating the vanes at their intake ends, and the width of the vanes at the intake ends is substantially double the width at the discharge ends, the cross sectional areas of the intake openings are substantially the same as-the cross sectional areas of the discharge openings. The result is that the moving column of air in. a channel between t1A vanes visnot compressed as itapproaches the discharge outlet, sincetthe column is moving through a channel of unchanging or substantially unchanging cross section with a constantlyincreasingv velocity. It will be evident that this condition necessarilyproduces a rarefaction or expansion of the vair column. In addition therelatively great peripheral separation of the discharge endsA of the blades permits of the formation of a partial vacuum immediately tothe rear of the moving blades and this partial vacuum has the effect of still further rarefying or attenuat ing the moving stream of air.

The result is that there can be no compressing of the stream of air advancing toward the discharge ends of. the blades. Instead, there is a rarefaction with an accompanying objectionable back lashing eiiectcaused by a vacuum formed in discharge ends of the 'spaces between the blades with a consequent loss of eiiiciency brought about ythrough the rehandling of a portion of the discharged air. The objectionableback lashing is very apparent in the operation of prior blowers of the pressure types, in which the outlet of the discharge openings, number of vanes, length of vanes and other factors are so chosen as to cause the apparatus to operate at a relatively high degree of eiiiciency with relation to the expenditure of power required for operation. More specifically, I so design the blades in their proportioning and relation to each other thatthe air streams passing through the` channels from the intake openings of the blades to the discharge ports thereof do not undergo rarefaction orexpansion in any degree, but, on the contrary, decrease in cross sectional area with the result that the streams emerge at the discharge ports of the vanes with the density of the mass of air fully re- `itored and even increased, and having had a velocity of travel imparted thereto which is exactly equal to the peripheral speed ofthe rotating wheel.

Other features of the invention will 'be hereinafter referred to.

In the drawings, in which one of many possible 4embodiments of the invention has been selected for illustration:

Fig. 1 is a view partly in front elevation and partly in vertical section of a blower of the pressure type embodying the invention;

Fig. 2 is a view in side elevation and partly .iin section of the device shown in Fig. 1.

Referring to the drawings for a more detailed description ofthe invention, a blower of the centrifugal type is shown in which a double rotor or fan Wheel 10 is mounted on a shaft 11 for rotation in a casing or housing 12. The .shaft 11 is journaled at 13 in the upper ends of suitable standards 14: and is provided with a driving pulley 15in a known manner.

The double fan wheelis provided with hub bracket members 16 .having radially extending flange portions 17 between which is clamped an annular web or frame pieceV 18 to Whichare riveted the inner edgesof a series of fan blades 19. A scrollfshaped housing 20 is mountedr on the peripheral portion of the housing 12 and vis provided with a discharge ortat 21 through which air is discharged om the blower into the manifold or conduit provided therefor. The discharge housing ,is

relatively slightly spaced apart relation as compared with the arrangementof blades in blowers heretofore known and used. For eX- 'i ample, in a fan wheel of twenty-seven inches in diameter, the size chosen for example and comparison, I find that the greatest efhciency is attained when forty-two blades or vanes are used, the separation of the blades at their discharge ends 21 being two inches, while the intake ends 22 of the blades, which are at a distance of six and three-quarter inches from the axis of rotation, are separated by a distance of only one inch.

The inletopening 23, which is supplied at either side of the double wheel, has a diameter equal to one-half the diameter of the wheel in the particular example shown'.

An important feature of the invention re* sides in the design of the blades which are, in the example shown, 6.75 inches wide at their intake end, measured between their wid-- est points 22 at the junction of the bladesv with the edge of the inlet opening 23. 'The width of `the discharge ends of 'the 'blades at 21 is, in the example shown, 1.;7 inches, so that the width of the .blades :at the-intake end is substantially four times ythe width -of the blades at the discharge end. With this proportioning of the vaneareas and distances separating-the individual blades, it will be seen that the channels between the Ablades have a cross sectional area of one times '6.75 or 6.75 square inches at their intake ends while at their Voutlet ends the same channels have a cross sectional area of -two times 1.7 or '3.4 square inches. In other words, 'the cross sectional area Vof the intake -ends of it-he channels is substantially twice the cross Asectional area v*of the discharge or outlet ends.

With this arrangement of structure it will be seen 'that the density Aof the ai-r streams moving through the channels formedbetween the vanes is so regulated that the initial lloss in density at the points `of entry of the .air into the channels 'and the tendency L'to further loss due to the increasing velocity of flow are wholly compensated for. 'The -effect of this is to restore or rebuild and to maintain the density of the air streams at substantially that ofthe atmosphere sojthat when the air streams emergent thev outlet ports 21 their density has not been impaired but, on the contrary, there is imparted -to the air streams the necessary pressure `to establish a velocity of flow equal to that of the peripheral speed of the wheel.

This useful arrangement which prevents the back lashing of air referred to with its r attendant loss of efficiency and at the sam-e time does not restrict the area of the outlet ports beyond that necessary to impart lto the 'flowing stream the necessary velocity and normal density, delivers the air into the housing for restriction therein to produce the desired pressure effects.

In order to more specifically compare my improved blower with a typical structure of the prior art, a standard prior art blower having a fan wheel diameter of 27 inches with s an inlet port of 13 inches diameter at each side, and with i3 vanes 6.75 inches wide at the intake end and 2.87 5 inches wide at the discharge end, is taken as a basis for comparison.

A standard type prior art blower having the dimensions and number of vanes referred to and operated at a peripheral speed of 16,000 feet per minute, will deliver per miuute into the enclosing shroud or housing approximately 5,720 cubic feet of air. Since the blowers under consideration are of the pressure type, it is necessary to produce a pressure effect in the mass of air delivered from the passages of the blower wheel into the housing. This pressure effect isordinarily produced by restricting the free passage of air from the housing by means of an appropriate restriction in the size of the housing discharge port. In the particular blower construction chosen for comparison a restriction of 39 per cent is produced in the volume of air passing through the housing thereby producing an ultimate discharge volume 'of 3,490 cubic feet per minute. Y

The prior art blower, thus described, is to be compared with a blower of applicants type having a fan wheel of the same diameter, 27 inches, and rotating at the same peripheral speed, 16,000 feet per minute. Applicants blower is provided with 42 vanes, as compared with 18 vanes in the prior art structure, the vanes having a width at their intake ends of 6.75 inches and a width of 1.7 inches at their discharge ends. A blower having this relationship of parts will deliver 7,854 cubic feet of air into the housing per minute, as compared with 5,720 cubic feet delivered by the prior art machine. A restriction of 43 per cent placed upon this volume, to produce the pressure conditions required, reduces the volume to 4,577 cubic feet per minute, this volume of air being handled at a saving of 25 to 33.3 per cent in horsepower as compared with the power required to operate the standard blower-construction of the prior art. In other words, my improved blower, as compared with prior blower constructions, move a greater volume of air, at a higher density, and without a proportionate increase in the input of power.

This substantial increase in eiiiciency' of applicants blower over the blowers known in the prior art isdue to the elimination of back lash and other diiculties encountered by the rarefaction of the air stream which occurred in the channels formed between the particular blades typical of the prior art. Not only did back lash effects occur because of the rarefaction due to the lack of proper convergence of the kdelivery channels but also, and in a considerable degree, because of the-excessive spacing apart of the vanes or blades which made up the fan wheel structure. As has already been pointed out, the excessive spacing of the blades aided in the production of partial vacuum effects immediately to the rear of each blade tip and this partial vacuum condition was an important factor in producing the objectionable back lash effects referred to through the addedy expansion or rarefaction of the air streams approaching the discharge ports.

While the characteristicsof atypical pressure blower have been -given,'a proportioning of blade areas to provide an improved eiiioiency in blowers of the boost-er type can also be readily achieved. A blower of this construction is placed within a conveying duct and since the kinetic energy expended in lilling the intake side of the wheel is convertible into useful work through assisting the velocity of flow through the duct, a blower of this type will operate at its best efficiency when the kinetic energy expended in filling the wheel rand propelling and compressing energy exerted by the wheel on the volume of air passing therethrough are equivalent to each other. This ratio can be best establish-ed when the diameter of ther inlet opening 1nA the booster blower is seventy per cent of thediameter of the wheel. With this proportioning ofthe inlet opening of the` blower to the diameter of the wheel, a capacity of`2.6 times the capacity ofl a blower constructed with an intake opening of iifty per cent of the diameter of the wheel is obtained.

When operating as yan evacuating blower,

the structure has two duties to perform, that is, the establishing of a filling stream of air at a density below that vof the natural atmosphere and the compressing of the air passing through the structure to the required density and discharging the air, thus compressed', into the natural atmosphere.` capacity of a blower of this type is limited to the area of the discharge ports at any given peripheral velocity and the capacity toill the channels at the outletports is determined by the degree of rarefaction of the air to be handled. With these considerations in mind, the length and width of the vanes can be properly proportioned to secure ciiicient results irrespective of the degree of rarefaction of. the air to be handled.

The invention is not confined to use with 'double fanwheel structures but similar improvements in design and efficiency of operation can be as readily accomplished in fan wheels'of the single inlet type. lt will be clear that the inlet barrel of a single inlet wheel must have double the depth of either inlet barrel ofa double inlet wheel of the same size in order to cause the single inlet wheel to operate at the same capacity as that of the double wheel.

It will be seen that a type of blower construction has been developed in which the number and areas of the vanes have been calculated in strict proportion to the volume lEO Theta handling 105,

of ,air :to lbe fhandled While 'the outlet fports have areas just suiicientto permit the volume of air to :be delivered at a velocity equal to the yperipheral velocity of the wheel. It will be clear that the diameter of the inlet opere ings may be varied in accordance with the Work :to be done and that the :peripheral speed of the wheel Will be increased to compensate for -the shorter length of the vanes `when the diameter of `the inlet opening is increased.

The terms and expressions which I have employed are used as terms of description and not Vof limitation, and I have no intentionfin the use ofsuch terms andexpressions, of excluding any mechanical equivalents of the yfeatures shown and described, or portions thereof, but recognize that various structural modifications are possible Within the scope of 'the invention claimed.

1. In a blowerfof the centrifugal type, a fan Wheel having radially extending vanes Whose number is Asuch and whose areas are so proportioned to the speed of rotation of the wheel and to the volume `of the air flow as to cause the air passing -vthrough the outlets of the fan wheel to travel at a velocity equal tothe peripheralvelocity of the Wheel.

2. In a `blower of the centrifugal type, a Lfan Wheel `having radially extending` vanes in which the ratio of the widths of the outletends of the kvanes to the widthsof the inlet lends is such that the vair passingthrough the outlets is compressedsuiciently to produce a Vvelocity of ylfiow therein equal to the .peripheral velocity of travel of the outlet end of the vanes.

.3'. VIn `a blower of the centrifugal type, a .fan wheel provided With .radially disposed channels, whose cross-sectionalareas decrease outwardly, the area at different points being inversely proportional .to the kradial distance 4from the axis of rotation.

4. In ka blower of the centrifugal type, a

v,fan Wheel provided with radially disposed channels,.the area at the exit end of the chanvnels being one-half the area at the admission fend thereof.

5. In a blower of the centrifugal type, a .rotatable fan Wheel having side .members and transverse vanes :forming radial channels, the side members converging outwardly toward each other at such an angle that the .area of the channels is inversely proportional to the radial distance from the axis of rotation, substantially as described.

f JOSEPH JOI-IN STOETZEL. 

